I. Field of the Invention
This invention relates to novel polycarbonate compositions formed by the reaction of aromatic trihydroxy phosphorus compounds to induce random-chain branching.
II. Description of the Prior Art
Branched-chain high-molecular weight thermoplastic polycarbonates containing the residues of monohydric phenols and polyhydric phenols having more than two hydroxy groups in the molecule are disclosed in U.S. Pat. No. 3,544,514 and its reissue U.S. Pat. No. Re. 27,682.
Other patents disclose polyphenolic compounds having utility as branching agents in the production of randomly-branched polycarbonates such as U.S. Pat. Nos. 3,094,508 and 4,426,513, however, none of these patents disclose the trihydroxy phosphorus compounds as branching agents of the present invention.
Polycarbonates having the phosphorus element in the backbone of the polymer are illustrated by U.S. Pat. No. 4,444,978. These polycarbonates have increased thermal stability. Other phosphorus-modified polycarbonate resins are disclosed in U.S. Pat. No. 4,474,937. Likewise, U.S. Pat. Nos. 4,322,520; 4,381,390; 4,481,350 and 4,508,890 each disclose phosphorus-modified polycarbonates. However, none disclose the trifunctional aspect of the present invention which provides the random branching.
U.S. Pat. No. 3,597,394 discloses that polycarbonates are branched or crosslinked by the addition of the cyclic trimer of phosphonitrilic chloride.